Polymorphic CAG repeats of the androgen receptor gene in Japanese male patients with ankylosing spondylitis

The role of an anterior approach in the treatment of ankylosing spondylitis-associated cervical fractures: a systematic review and meta-analysis

OBJECTIVE

Cervical fractures in patients with ankylosing spondylitis can have devastating neurological consequences. Currently, several surgical approaches are commonly used to treat these fractures: anterior, posterior, and anterior-posterior. The relative rarity of these fractures has limited the ability of surgeons to objectively determine the merits of each. The authors present an updated systematic review and meta-analysis investigating the utility of anterior surgical approaches relative to posterior and anterior-posterior approaches.

METHODS

After a comprehensive literature search of the PubMed, Cochrane, and Embase databases, 7 clinical studies were included in the final qualitative and 6 in the final quantitative analyses. Of these studies, 6 compared anterior approaches with anterior-posterior and posterior approaches, while 1 investigated only an anterior approach. Odds ratios and 95% confidence intervals were calculated where appropriate.

RESULTS

A meta-analysis of postoperative neurological improvement revealed no statistically significant differences in gross rates of neurological improvement between anterior and posterior approaches (OR 0.40, 95% CI 0.10-1.59; p = 0.19). However, when analyzing the mean change in neurological function, patients who underwent anterior approaches had a significantly lower mean change in postoperative neurological function relative to patients who underwent posterior approaches (mean difference [MD] -0.60, 95% CI -0.76 to -0.45; p < 0.00001). An identical trend was seen between anterior and anterior-posterior approaches; there were no statistically significant differences in gross rates of neurological improvement (OR 3.05, 95% CI 0.84-11.15; p = 0.09). However, patients who underwent anterior approaches experienced a lower mean change in neurological function relative to anterior-posterior approaches (MD -0.46, 95% CI -0.60 to -0.32; p < 0.00001). There were no significant differences in complication rates between anterior approaches, posterior approaches, or anterior-posterior approaches, although complication rates trended lower in patients who underwent anterior approaches.

CONCLUSIONS

The results of this review and meta-analysis demonstrated the varying benefits of anterior approaches relative to posterior and anterior-posterior approaches in treatment of cervical fractures associated with ankylosing spondylitis. While reports demonstrated lower degrees of neurological improvement in anterior approaches, they may benefit patients with less-severe injuries if lower complication rates are desired.

Genetics, Epigenetics, and Gender Impact in Axial-Spondyloarthritis Susceptibility: An Update on Genetic Polymorphisms and Their Sex Related Associations

Spondyloarthritis (SpA) is a group of chronic inflammatory rheumatic disease that can be divided into predominantly axial or predominantly peripheral involvement, with or without associated psoriasis, inflammatory bowel disease or previous infection. Axial SpA (axSpA) encompasses ankylosing spondylitis (AS) with radiological sacroiliitis, and a type without radiographic sacroiliitis, called “non-radiographic axial SpA” (nr-axSpA). Males and females show large differences in their susceptibility to SpA, such as distinctions in clinical patterns, phenotypes and in therapeutical response, particularly to TNF inhibitors (TNFi). Several studies indicate that AS women have doubled risk to failure TNFi compared with males. This diversity in drugs’ efficacy among women and men may be caused by differences in the balance of sex hormones and in gene-specific expression likely triggered by X-chromosome instability and gene-specific epigenetic modifications. Evidence reported that polymorphisms in microRNAs on X- and other chromosomes, such as miR-146a, miR-155, miR-125a-5p, miR-151a-3p and miR-22-3p, miR-199a-5p could be involved in the different clinical presentation of SpA, as well as disease activity. In addition, association with non−response to TNFi treatment and presence of IRAK3 and CHUCK genes in SpA patients was recently detected. Finally, polymorphisms in genes involved in IL-23/IL-17 pathway, such as in drug pharmacodynamics and pharmacokinetics may have a role in response to TNFi, IL17i, and IL23i. A major understanding of genomic variability could help in the development of new therapeutic targets or in taking advantages of different mechanisms of action of biological drugs. Moving from the multifactorial etiology of disease, the present review aims at evaluating genetic and epigenetic factors and their relationship with sex and bDMARDs response, helping to investigate the different expression among males and females of genes on X- and other chromosomes, as well as mi-RNA, to highlight relationships between sex and occurrence of specific phenotypes and symptoms of the disease. Moreover, the role of the epigenetic modification in relation to immune-regulatory mechanisms will be evaluated.

Sex steroids and autoimmune rheumatic diseases: state of the art

In autoimmune rheumatic diseases, oestrogens can stimulate certain immune responses (including effects on B cells and innate immunity), but can also have dose-related anti-inflammatory effects on T cells, macrophages and other immune cells. By contrast, androgens and progesterone have predominantly immunosuppressive and anti-inflammatory effects. Hormone replacement therapies and oral contraception (and also pregnancy) enhance or decrease the severity of autoimmune rheumatic diseases at a genetic or epigenetic level. Serum androgen concentrations are often low in men and in women with autoimmune rheumatic diseases, suggesting that androgen-like compounds might be a promising therapeutic approach. However, androgen-to-oestrogen conversion (known as intracrinology) is enhanced in inflamed tissues, such as those present in patients with autoimmune rheumatic diseases. In addition, it is becoming evident that the gut microbiota differs between the sexes (known as the microgenderome) and leads to sex-dependent genetic and epigenetic changes in gastrointestinal inflammation, systemic immunity and, potentially, susceptibility to autoimmune or inflammatory rheumatic diseases. Future clinical research needs to focus on the therapeutic use of androgens and progestins or their downstream signalling cascades and on new oestrogenic compounds such as tissue-selective oestrogen complex to modulate altered immune responses.

Androgen receptor genetic variants in male patients with ankylosing spondylitis in Taiwan

AIM

Ankylosing spondylitis (AS) is a chronic rheumatic disorder with gender differences. The aim of study was to investigate the association between polymorphisms of the androgen receptor (AR) gene and the susceptibility to AS in Taiwanese men of Han Chinese descent.

METHODS

We conducted a case-control study with 92 male AS patients and 108 healthy controls. Trinucleotide (CAG and GGC) repeats and seven single nucleotide polymorphisms (SNPs) rs962458, rs6152, rs1204038, rs5918757, rs2361634, rs6624304 and rs1337080 in the AR gene were genotyped.

RESULTS

We found that only one patient had polymorphic SNPs of the AR gene. None of the genotyped SNPs in the AR gene, originally found in Caucasians, was polymorphic in the Taiwanese men. Neither CAG nor GGC repeat lengths in the AR gene had a significant relationship with human leukocyte antigen (HLA)-B27 positivity or disease severity in AS.

CONCLUSION

There were no differences in CAG and GGC lengths in the AR gene between AS and the controls. None of the genotyped SNPs in AR gene are detected to be polymorphic in male Taiwanese, which indicates that the effect of AR gene on AS may be ethnic-specific and may be conserved in East Asians compared to Caucasian populations. Still, additional studies using large sets of subjects deserve further attention, since our sample size was small with limited statistical power and supporting evidence for association between the AR gene and AS risk in the Japanese population exists.

The genetic basis of ankylosing spondylitis

PURPOSE OF REVIEW

Genetic factors provide over 90% of the overall susceptibility to ankylosing spondylitis, with about half of the genetic contribution attributed to HLA-B27 and other major histocompatibility complex genes. Recent studies have focused on non-major histocompatibility complex genes. This review is aimed at summarizing the status of major histocompatibility complex and non-major histocompatibility complex genes in ankylosing spondylitis susceptibility, and suggests areas for future studies.

RECENT FINDINGS

A recent meta-analysis of published scans of ankylosing spondylitis susceptibility has confirmed sites on chromosomes 3q, 6p (the major histocompatibility complex), 10q, 16q and 19q in ankylosing spondylitis susceptibility. Non-major histocompatibility complex candidate gene analyses have confirmed a role for the IL-1 gene complex. The search for other non-major histocompatibility complex candidate genes, however, has been complicated by inadequate power in most previous studies. Innovations in genetic methodologies will allow thorough genome wide linkage disequilibrium mapping studies in large cohorts of patients that will result in the dissection of the genetic susceptibility to ankylosing spondylitis.

SUMMARY

Nearly half of the susceptibility to ankylosing spondylitis is provided by major histocompatibility complex genes. Non-major histocompatibility complex genes, most notably the IL-1 gene complex, have been identified and novel technologies promise that a more thorough examination of the rest of the genome will soon elucidate the genetic basis of this disease.

Androgen receptor trinucleotide polymorphism in leiomyoma

OBJECTIVE

Androgen receptor (AR) was detected in leiomyoma. AR gene has a polymorphic microsatellite encoding cytosine, adenine, and guanine (CAG) repeats. We aimed to investigate the association between the AR gene CAG repeats and leiomyoma.

METHODS

Women were divided into two groups: (1) leiomyoma (n = 159); (2) non- leiomyoma groups (n = 129). Their CAG repeats were detected by polymerase chain reaction. The CAG repeats ranged in length from 168 bp (9 CAG repeats, genotype A) to 234 bp (31 CAG repeats, genotype W). Distributions of CAG repeats in both groups were compared.

RESULTS

Genotype proportions of different CAG repeats for AR gene in both groups were significantly different. The genotype S (27 CAG repeats) is associated with higher susceptibility of leiomyoma. Distribution of CAG repeats in both groups appeared mono-peak distributions. Percentages of genotypes K-S (19-27 CAG repeats) in leiomyoma and non-leiomyoma groups were: (1) 5,11,19.5, 10.4, 12.9, 8.8, 7.5, 5.7, 4.4%; (2) 5.4, 14.3,16.7, 12.8, 12.4, 5.8, 9.3, 7,1.2%.

CONCLUSIONS

AR trinucleotide polymorphism is associated with leiomyoma susceptibility. The 27 CAG repeats is related with higher risk of leiomyoma.

Spondyloarthritis: update on pathogenesis and management

A great deal of progress has occurred in the past few years in elucidating the causes and designing new treatments for ankylosing spondylitis and other types of spondyloarthritis. In addition to the human leukocyte antigen (HLA)-B27 and other major histocompatibility complex (MHC) genes, chromosomal regions and genes elsewhere in the genome are being implicated both in disease susceptibility and severity. The various ways HLA-B27 may function in causing spondyloarthritis now are better understood to encompass not only antigen presentation but also other mechanisms, possibly all being operative in pathogenesis (misfolding of the HLA-B27 molecule, impaired intracellular killing of bacteria, and HLA-B27 itself serving as an autoantigen). Specific enteric and sexually acquired infections can trigger reactive arthritis, though no specific microbe has been identified in other forms of spondyloarthritis. Intestinal inflammation with impairment of the gut:blood barrier may be operative in driving ankylosing spondylitis and enteropathic arthritis. A number of treatments have been tried in spondyloarthritis, including older agents such as methotrexate and sulfasalazine but also newer drugs such as pamindronate. The recent introduction of tumor necrosis factor (TNF) blockers in the treatment of spondyloarthritis has offered the most hope in not only relieving symptoms and signs of both peripheral arthritis and enthesitis but also spinal disease, which often has been refractory to other agents. Their high cost and considerable side effect profile, however, have necessitated the establishment of guidelines for their use in these diseases in order to target the patient in whom they are likely to have the most benefit.

The genetic basis of spondyloarthritis

Spondyloarthritis tends to cluster in families and, to a great extent, is associated with human leukocyte antigen (HLA) B27. In fact, the population frequency of spondyloarthritis in most groups is proportional to that of HLA-B27. But the frequency of HLA-B27 in the population-at-large far exceeds that of spondyloarthritis, suggesting other genetic factors also are operative. Other major histocompatibility complex genes have been implicated, especially HLA-DR, though linkage to HLA-B27 confounds the analysis of this in many studies. Genome-wide scans have implicated regions on chromosomes 2q, 6p, 6q, 10q, 11q, 16q, 17q, and 19q in ankylosing spondylitis, on 4, 6p, and 17q in psoriasis, and on 7q and 16q in inflammatory bowel disease. The search for non-major histocompatibility complex candidate genes has been complicated by inadequate power, because of the small effect they exert on overall disease susceptibility, although recent studies are revealing promising candidates that must be confirmed by other groups.

Ankylosing spondylitis: an overview

Ankylosing spondylitis (AS) is a complex, potentially debilitating disease that is insidious in onset, progressing to radiological sacroiliitis over several years. Patients with symptomatic AS lose productivity owing to work disability and unemployment, have a substantial use of healthcare resources, and reduced quality of life. The pathogenesis of AS is poorly understood. However, immune mediated mechanisms involving human leucocyte antigen (HLA)-B27, inflammatory cellular infiltrates, cytokines (for example, tumour necrosis factor alpha and interleukin 10), and genetic and environmental factors are thought to have key roles. The detection of sacroiliitis by radiography, magnetic resonance imaging, or computed tomography in the presence of clinical manifestations is diagnostic for AS, although the presence of inflammatory back pain plus at least two other typical features of spondyloarthropathy (for example, enthesitis and uveitis) is highly predictive of early AS. Non-steroidal anti-inflammatory drugs (NSAIDs) effectively relieve inflammatory symptoms and are presently first line drug treatment. However, NSAID treatment has only a symptomatic effect and probably does not alter the disease course. For symptoms refractory to NSAIDs, second line treatments, including corticosteroids and various disease modifying antirheumatic drugs, are employed but are of limited benefit. Emerging biological therapies target the inflammatory processes underlying AS, and thus, may favourably alter the disease process, in addition to providing symptom relief.

The ratio of 2nd to 4th digit length: a proxy for transactivation activity of the androgen receptor gene?

The androgen receptor gene (AR) contains a domain which includes a variable number of CAG sequences and alleles with low numbers of CAG repeats show high transactivation activity when complexed with testosterone. The ratio of 2nd and 4th digit length (2D:4D) is negatively correlated with phenotypic effects of testosterone. Low numbers of CAG repeats and low 2D:4D are both associated with high sperm numbers and protection against breast cancer. This suggests that CAG number and 2D:4D are correlated i.e. low CAG number and low 2D:4D indicate high activation of androgen-responsive genes. Findings from AR studies predict that low 2D:4D will be associated with prostate and hepatocellular cancer, urolithiasis, ADHD, ankylosing spondylitis, spontaneous abortion, and polycystic ovaries, while high 2D:4D will be associated with motor neuron diseases and endometrial cancer. Findings from 2D:4D studies predict that short CAG length will be common in autism and Asperger's syndrome, while high numbers of CAG repeats will be found in men who are prone to early myocardial infarction.

HLA-B27 and genetic predisposing factors in spondyloarthropathies

With the mapping of the human genome having been completed, our ability to investigate and ideally better understand the genetic basis of rheumatic diseases is advancing at a rapid pace. Substantial evidence strongly favors a direct role for HLA-B27 in genetic susceptibility to ankylosing spondylitis and related spondyloarthropathies, although the underlying molecular basis has yet to be identified. HLA-B27 contributes only 16 to 50% of the total genetic risk for the disease, clearly indicating that other genes must be involved. However, no other putative disease genes have yet been absolutely proven. Potential genes include MHC (HLA class II, low molecular weight proteasome [LMP], transporter associated with antigen processing (TAP), tumor necrosis factor [TNF]-alpha, and major histocompatibility complex class I chain-related gene A (MICA), as well as non-MHC genes (IL-1RA, IL-6, IL-10, and CYP2D6). Genome-wide screens have identified other chromosomal areas of interest: 1p, 2q, 6p, 9q, 10q, 16q, and 19q. However, different studies have given conflicting results. HLA-B27 itself is a serologic specificity, which encompasses 25 different alleles that encode 23 different products (proteins): HLA-B*2701 to B*2723. These alleles may have evolved from the most widespread subtype, B*2705, and two of them, B*2706 in Southeast Asia and B*2709 in Sardinia, seem not to be associated with ankylosing spondylitis. The distinction between the disease associated and nonassociated subtypes may provide clues to the actual role of B27 in disease pathogenesis.